Twin-scroll turbocharger

Abstract

A twin-scroll turbocharger comprises front and rear scrolls, a scroll throat portion separating the scrolls, a rotor blade rotated by exhaust gas, and a turbine housing forming, with an outer circumferential portion of the rotor blade, the front scroll and the rear scroll, and including an inclined surface on which an extended line of the incline facing toward the scroll throat portion of the front scroll and an inlet of the rotor blade intersect at a position in a central portion of the inlet of the rotor blade, wherein the connection R at a crossing portion P where the inclined surface and an inner periphery surface of the turbine housing intersect has a shape such that the gap of a constant width a continues to the position of the inlet of the rotor blade.

The invention claimed is: 
     
       1. A twin-scroll turbocharger configured to be driven by exhaust gas of an engine, comprising:
 a turbine housing of a turbocharger, 
 two exhaust gas introducing passages comprising a front scroll and a rear scroll, each of which is formed in the turbine housing along an axis line of a rotatable shaft of the turbocharger, 
 a separation wall configured to separate the rear scroll and the front scroll, and 
 a rotor blade mounted to the rotatable shaft and configured to rotate the rotatable shaft by exhaust gas, wherein 
 the rear scroll is disposed so that a center line on a cross-sectional surface along a radial direction is substantially perpendicular to the axis line, 
 the front scroll is disposed so that a center line on a cross-sectional surface along a radial direction has a gradient toward a side of an outlet of the rotor blade with respect to the axis line, 
 an extended line of an inclined surface of the front scroll on a side of the housing and an inlet of the rotor blade intersect at a position in a central portion of the inlet of the rotor blade, and 
 the front scroll has an outlet portion formed so that a crossing portion at which the inner periphery surface of the turbine housing, having a gap of a constant width between the inner periphery surface and an outer circumferential portion of the rotor blade, and the extended line of the inclined surface intersect is at a position within a width of the inlet of the rotor blade and further away from the axis in a radial direction than the inlet of the rotor blade, and 
 wherein an area of a flow path in an inlet portion of the rotor blade is expanded relative to an area of an outlet of one of the rear scroll or the front scroll, and an area of the outlet of the rotor blade is expanded relative to the area of the flow path in the inlet portion of the rotor blade, and wherein an area expansion rate of the area of the flow path in the inlet portion of the rotor blade to the area of an outlet of one of the rear scroll or the front scroll and an area expansion rate of the area of the outlet of the rotor blade to the area of the flow path in the inlet portion of the rotor blade are substantially the same. 
 
     
     
       2. The twin-scroll turbocharger according to  claim 1 , wherein a ratio of a width, in a direction of the rotational axis, of the flow path in the inlet portion of the rotor blade to a width, in the direction of the rotational axis, of the outlet of one of the rear scroll or the front scroll is from 1.2 to 1.4. 
     
     
       3. The twin-scroll turbocharger according to  claim 2 , wherein a connecting portion where the inner periphery surface of the turbine housing and the inclined surface are connected is formed in an arc-like shape, and the center of the arc-like shape is, in the radial direction, on the same position as the inlet of the rotor blade or on a position farther than the inlet of the rotor blade from the axis line of the rotatable shaft. 
     
     
       4. The twin-scroll turbocharger according to  claim 1 , wherein a connecting portion where the inner periphery surface of the turbine housing and the inclined surface are connected is formed in an arc-like shape, and the center of the arc-like shape is, in the radial direction, on the same position as the inlet of the rotor blade or on a position farther than the inlet of the rotor blade from the axis line of the rotatable shaft.